3.3.3 HR 用户下建一张表T1 模拟问题
先插入27 条数据，后删除7 条数据，最后truncate 这张表，要求把数据恢复到20 条数据的状态。
SQL> connect hr/hr Connected. SQL> show user USER is "HR" SQL> create table T1 tablespace users 2 as select * from departments; Table created. SQL> select count(*) from T1; COUNT(*) ---------- 27 SQL> select dbms_flashback.get_system_change_number from dual; GET_SYSTEM_CHANGE_NUMBER ------------------------ 111349 SQL> delete from hr.T1 where department_id>200; 7 rows deleted. SQL> commit; Commit complete. SQL> select count(*) from hr.T1; COUNT(*) ---------- 20 SQL> select dbms_flashback.get_system_change_number from dual; GET_SYSTEM_CHANGE_NUMBER ------------------------ 111391 SQL> SQL> truncate table hr.T1; Table truncated. SQL> select count(*) from hr.T1; COUNT(*) ---------- 0 SQL>
SCN 为111391 时HR.T1 中的数据为20 条。
